Seal construction for pump apparatus

ABSTRACT

An endless path calibration system comprising a sensor cassette having a flow-through passage and at least one sensor to be calibrated, a chamber coupled to the sensor cassette to define an endless path and a sterile calibration liquid in the endless path. A gas injection passage for injecting gas into the sterile calibration liquid and a gas vent leading from the endless path to the exterior of the endless path. A check valve allows gas to escape from the endless path and substantially prevents gas and liquid from entering the endless path through the gas vent.

The present application is a divisional of U.S. Pat. application Ser.No. 07/514,704, filed Apr. 26, 1990 now U.S. Pat. No. 5,057,278.

BACKGROUND OF THE INVENTION

It is often necessary or desirable to monitor various parameters ofblood and to obtain quantitative data concerning such parameters in realtime. In order to accomplish this, blood is caused to flow through aflow-through housing past sensors which provide signals representativeof the parameters of interest. For example, Cooper U.S. Pat. No.4,640,820 shows a flowthrough housing with fluorescent sensors whichrespond to the partial pressure of oxygen, the partial pressure ofcarbon dioxide and the pH of blood which has passed through theflow-through housing.

Prior to using the flow-through housing, the sensors must be calibrated.One calibration technique, which is used for the sensors of the Cooperpatent, is to attach the sensor carrier to a calibration housingcontaining calibration liquid. This places the sensors in communicationwith a relatively large cross-sectional area passage. The gas or gasesof interest are then bubbled through the calibration liquid. A similartechnique is utilized to calibrate the sensors shown in Maxwell U.S.Pat. No. 4,830,013.

This calibration technique, which employs an essentially staticcalibration liquid, is most satisfactory when used in conjunction withsensors adjacent a passage of sufficient cross-sectional area so thatthe calibration liquid remains in the passage while the gases are passedthrough the liquid. Because the sensors must be kept wet, a gas-onlycalibration technique cannot be employed.

For some applications, it is desirable to utilize a flow-through housinghaving a relatively small cross-sectional area and to maintain that areasterile during calibration. In fact, the cross-sectional area issufficiently small so that, when gas is passed through the liquid, thesurface tension may cause the calibration liquid to be expelled from thepassage and prevent exposure of the sensors to the gases in thecalibration liquid and thus cause an inaccurate calibration.

SUMMARY OF THE INVENTION

This invention solves the problems identified above. With thisinvention, sterile calibration liquid is equilibrated with the gas ofinterest and then pumped through the flow-through passage, therebyassuring that adequate calibration liquid will fill the flow-throughpassage. In addition, the sterile calibration liquid is pumped through asterile-loop calibration system. The sterile calibration loop providesan endless path for circulation of the sterile calibration liquid. Theprovision of an endless path eliminates the need to replenish thecalibration liquid supply and the need to dump any of the liquid todrain. This also enhances the sterility of the calibration operation. Inaddition, openings in the loop which could cause a break in thesterility barrier are minimized.

The commonly used blood gas sensors sense oxygen and carbon dioxide,respectively. In order to calibrate O₂ and CO₂ sensors, it is necessaryto control, i.e., raise or lower, the partial pressures of these twogases in the calibration liquid until they reach a known desired level.With this invention, this is brought about by injecting a sterile gasinto the sterile loop. The sterile gas contains known percentages byvolume of oxygen and CO₂.

The sterile gas is mixed with the sterile calibration liquid in thesterile loop to adjust or control the partial pressure of at least acomponent, e.g , O₂ or CO₂, of the gas in the sterile calibrationliquid. To enable a continuous supply of fresh gas without anundesirable pressure build up in the loop, the gas is vented from thesterile loop. By pumping the sterile calibration liquid having the CO₂and O₂ dissolved therein through the sterile loop and exposing thesensors to this calibration liquid, calibration can occur using knowntechniques.

More specifically, the sterile-loop calibration system includes a sensorcassette having a flow-through passage and including at least one sensorto be calibrated. The sensor is responsive to a characteristic of a gas,such as the partial pressure of O₂ or CO₂. The flow-through passageforms a portion of the sterile loop. To further guard against loss ofsterility, a sterile calibration liquid is provided in the sterile loopat the factory so that the user need not do this.

To accomplish gas injection, a gas injection passage is provided throughwhich a gas can be injected into the sterile calibration liquid. Tocontrol the partial pressures of the gases of interest in the sterilecalibration liquid to a desired level, means is provided in the sterileloop for mixing the gas and the calibration liquid. Although such meansmay take different forms, it may advantageously include a region, suchas a chamber, in the sterile loop of increased volume which reduces flowvelocity and, therefore, provides more time for equilibration. Toaccomplish venting of the gas, a gas vent leading from the sterile loopto the exterior of the sterile loop is provided.

Sterility through the vent can be provided in different ways. Forexample, means may be provided in the vent for allowing gas to escapefrom the sterile loop and to substantially prevent gas and/or liquidfrom entering the sterile loop through the gas vent. Alternatively, orin addition thereto, the vent may include or define a small areaflow-restricting orifice. If no check valve is used, the orifice shouldbe closed or covered after calibration. Sterility can also be enhancedby maintaining the pressure in the loop above atmospheric so that thereis a differential pressure across the gas vent tending to allow gas toescape and precluding gas entry through the vent into the sterile loop.

If desired, a source of sterile gas may be provided for injection intothe sterile loop through the gas-injection passage. However, preferably,a gas-sterilizing filter is provided in communication with the gasinjection passage for sterilizing the gas injected into the sterileloop. This eliminates the need for providing a separate source ofsterilized gas at the user's facility.

The chamber preferably includes a sparging chamber section and asettling chamber section. The sparging chamber serves primarily as amixing chamber and provides time for the partial pressure of the gasesof interest to equilibrate to the desired level. In the settlingchamber, bubbles are given an opportunity to rise to the top and bevented. Accordingly, the vent preferably terminates in the settlingchamber. In one preferred construction, the chamber includes a weir ordivider which divides the chamber into the sparging chamber section andthe settling chamber section. A baffle adjacent the weir and in thesparging chamber can advantageously be provided for optimizing bubblesize in the calibration liquid.

In a preferred construction, the gas is injected into the calibrationliquid in the sterile loop upstream of the chamber and then passed tothe chamber. This provides some opportunity for mixing of the gas andthe liquid before they reach the chamber and helps to provide relativelysmall gas bubbles in the chamber. Preferably, the gas-injection passageis oriented relative to the sterile loop so that the gas is directedinto the sterile loop substantially at a location in the sterile loopwhere the flow of sterile calibration liquid is changing direction. Thiscan be accomplished, for example, by a "T" connection.

The sterile loop of this invention is preferably a closed liquid loop inthat no liquid is added to the loop during operation, and little, oressentially no, liquid is drained from the loop. Although a gas is addedand vented and some small quantity of liquid may escape through thevent, it is relatively easy to assure that the gas is sterile by usingthe sterilizing filter, and the venting of the gas and possibly smallamounts of liquid through an orifice or a check valve help maintain theloop effectively closed. Moreover, there is no need to collect thevented gas.

In a preferred construction, a number of the components of thecalibration system can be provided within, or as a part of, acalibration housing. The calibration housing has an inlet, an outlet anda liquid passage extending through the housing from the inlet to theoutlet. Conduit means couples the opposite ends of the flow-throughpassage of the sensor cassette to the inlet and the outlet,respectively, of the housing to form the sterile loop. The chamber, gasinjection passage and gas vent are all provided on the housing.

It is desirable to monitor the temperature of the calibration liquid andto maintain it at a desired temperature. For this purpose, the housinghas a temperature sensing location, which can advantageously be atemperature well, adapted to cooperate with a temperature probe.Although the temperature well can be in heat-exchange relationship withany part of the sterile loop, preferably it is in heat exchangerelationship with an outlet passage section leading from the settlingchamber to the outlet of the housing. This location keeps thetemperature sensor well on the housing and as close to the sensorcassette as possible.

In a preferred construction, the liquid passage includes a radiallycompressible tube which is progressively compressed in a manner toachieve peristaltic pumping action. The tube is wrapped in acircumferential direction at least part way around the tube compressor.The tube has opposite end portions which extend generally tangentiallyof the tube compressor and then axially of the tube compressor to theirrespective ends. By turning the end portions of the tube to extendgenerally axially of the tube compressor, the number of parts requiredfor the housing are reduced, assembly is facilitated and the spacerequired for the housing is reduced.

However, because the end portions of the tube are turned in thisfashion, it is necessary to seal the ends of the tube to other portionsof the housing. More particularly, the housing passage includes firstand second passage sections, and means is provided for sealing the endsof the tube to the first and second passage sections, respectively. In apreferred form, this seal construction employs a rigid ring which isloaded against a deformable flange of the tube by a portion of thehousing which contacts the rigid ring around less than 360 degrees tosqueeze the flange and achieve the desired seal. Another feature of thisinvention is a novel seal construction for sealing the ends of this tubeto portions of the housing.

The invention, together with additional features and advantages thereof,may best be understood by reference to the following description takenin connection with the accompanying illustrative drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic illustration of a sterile-loop calibration systemconstructed in accordance with the teachings of this invention.

FIG. 1A is a sectional view taken generally along line 1A--1A of FIG. 1and illustrating one form of sensor cassette.

FIG. 2 is a plan view with portions broken away of a preferred form ofcalibration housing constructed in accordance with the teachings of thisinvention.

FIGS. 3 and 4 are enlarged sectional views taken generally along lines3--3 and 4--4, respectively, of FIG. 2.

FIG. 4A is an enlarged fragmentary sectional view of a portion of FIG. 4illustrating a preferred form of the novel seal construction of thisinvention.

FIG. 5 is an enlarged fragmentary sectional view taken generally alongline 5--5 of FIG. 2.

FIG. 6 is an enlarged fragmentary sectional view taken generally alongline 6--6 of FIG. 2.

FIG. 7 is a fragmentary perspective view illustrating the calibrationsystem and, in particular, the calibration apparatus, with the housingin a package and the door of the calibration apparatus in the openposition.

FIG. 8 is a perspective view similar to FIG. 7, with the door in theclosed position.

FIGS. 9, 10 and 11 are enlarged fragmentary sectional views takengenerally along lines 9--9, 10--10 and 11--11, respectively, of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a sterile-loop calibration system 11 which generallycomprises a sensor cassette 13, a calibration housing 15, sterilecalibration liquid 16, and conduit means, including conduits 17 and 19,for coupling the calibration housing to the sensor cassette. Notillustrated in FIG. 1, but also included in the calibration system, is acalibration apparatus 21 (FIG. 7). The portion of the system shown inFIG. 1 is a disposable component or apparatus and is designed for usewith the calibration apparatus 21, which is a reusable component.

The sensor cassette 13 may be of the type shown in common assignee'sco-pending application Ser. No. 229,617 filed on Aug. 8, 1988, andentitled Intravascular Blood Gas Sensing System (now U.S. Pat. No.4,989,606), which is incorporated by reference herein. Briefly however,the sensor cassette 13 includes a flow-through passage 23 (FIG. 1A)having first and second ends in the form of tube fittings 25 and 27which are joined to the conduits 17 and 19, respectively. Sensors 29, 31and 33, which are to be calibrated, are carried by the sensor cassettein communication with the flow-through passage 23. The sensors 29, 31and 33 may be, for example, for sensing carbon dioxide, pH and oxygen,respectively, and each of these sensors is covered by a membrane 35which is permeable to the constituent of interest as described inapplication Ser. No. 229,617 referred to above. The flow-through passage23 has a very small cross-sectional area and may be, for example,rectangular and have dimensions of about 0.015 inch×0.164 inch.

The calibration housing 15 (FIGS. 1 and 2) has an inlet 37, an outlet 39and a liquid passage 41 extending through the housing from the inlet tothe outlet. The liquid passage 41 includes a chamber 43, which isdivided by a weir 45 or divider into a sparging chamber section 47 and asettling chamber section 49.

The flow-through passage 23, the conduits 17 and 19, and the liquidpassage 41 form a sterile loop which provides an endless loop in whichthe sterile calibration liquid 16 can be circulated.

The housing 15 has a gas injection passage 51 leading from a gasinjection port 52 to a location in the liquid passage 41 for injectinggas into the liquid passage and means in the form of a threaded closurecap 53 (FIGS. 2 and 3) for closing the gas-injection port. The housing15 also includes a gas vent 55 which, in this embodiment, includes arestricted orifice 56 having, for example, a diameter of about 1/16inch. The gas vent 55 leads from the settling chamber 49 to the exteriorof the housing. The gas vent 55 may be completely closed by a closurecap 57 (FIGS. 2 and 5). A check valve 59 (FIG. 5) in the gas vent 55allows gas to escape from the settling chamber 49 and substantiallyprevents gas from entering the chamber through the gas vent 55.

The construction of the housing 15 can best be understood by referenceto FIGS. 2-6. Although various constructions are possible, as shown inFIG. 3, the housing 15 includes a housing 61 of multiple molded plasticcomponents, such as a base 63, a cover 65 and a top section 67. At leastthe cover 65 and the top section 67 are preferably transparent. The base63, the cover 65 and the top section 67 may be suitably coupled togetheras with an adhesive.

As shown in FIGS. 2 and 6, the inlet 37 leads to an inlet passagesection 69 of the liquid passage 41. A radially compressible tube 71(FIG. 4) communicates with the inlet passage section 69 through anaperture or opening 73 in the cover section 65 and with a chamber inletsection 75 (FIGS. 2 and 4) through an aperture or opening 77 (FIG. 4)which also is in the cover 65. Thus, compressible tube 71 forms part ofthe fluid pathway within apparatus 11. The chamber inlet section 75leads to the sparging chamber 47 as shown in FIG. 2.

The gas injection passage 51 (FIG. 3) is defined in part by anexternally threaded tube 79 affixed to the top section 67. Agas-sterilizing filter 81 is supported on the cover 65 and retained inplace by a spider section 82 of the top section 67. The gassterilizingfilter 81 may be, for example, a 0.2 micron pore filter which is capableof sterilizing gas which passes through it due to the small pore size.Accordingly, with the cap 53 removed, a non-sterile gas can beintroduced as described below to the injection port 52 whereby it willpass through the filter 81, an aperture 83 in the cover 65, and apassage section 85 of the gas injection passage between the base 63 andthe cover 65 to the chamber inlet section 75 as shown in FIGS. 2 and 3.The chamber inlet section 75 forms a right angle (FIG. 2), and thepassage section 85 enters the apex of the right angle to form a "T" 84.Thus, the gas is injected into the liquid at a location where thedirection of flow of the liquid is changing. For example, the gasinjected into the gas injection passage 51 may comprise CO₂, O₂ and aninert gas, such as nitrogen.

With this construction, the sterile calibration liquid 16, with the gastherein, is introduced into the sparging chamber 47. The "T" 84 providesa premixing of the gas and liquid. As shown in FIG. 2, the base 63preferably has a baffle 86 adjacent the weir 45 and above the locationwhere the chamber inlet section 75 opens into the sparging chamber 47for the purpose of breaking up larger bubbles that may exist in theliquid. The sparging chamber 47 provides time for the gas to equilibratein the calibration liquid 16, and as liquid fills the sparging chamber,it is allowed to flow over the free end 87 of the weir 45 and fall intothe settling chamber 49. As gas bubbles through the calibration liquid16 in the sparging chamber 47, foam is generated and also flows over theweir 45 into the settling chamber 49. In the settling chamber 49, anyremaining gas bubbles are given another opportunity to rise to the topand be vented through the vent 55, which is in the form of an aperturein the cover 65 as shown in FIG. 5. A baffle 89 may be provided adjacentthe vent 55 to reduce the likelihood that the liquid component of anyfoam will exit through the vent 55.

Although various constructions are possible, in the form shown in FIG.5, the check valve 59 is conventional and is retained in a recess 91 inthe cover 65 by an externally threaded tube 93 affixed to the cover. Thecap 57 is threadedly attached to the tube 93.

As shown in FIG. 2, the liquid passage 41 also includes an outletpassage section 95 leading from the settling chamber 49 to the outlet39. The housing 15 has a temperature sensing location which, in thisembodiment, is in the form of a temperature well 97 adapted to receive atemperature probe in heat exchange relationship with the outlet passagesection 95 as shown in FIG. 3. Although various constructions arepossible, the outlet passage section 95 may communicate with thesettling chamber 49 through an aperture 99 as shown in FIG. 2. Theaperture 99 is positioned to force flow to occur around the temperaturewell 97.

In order to move the calibration liquid 16 through the sterile loop, itis necessary to provide a pump to force the calibration liquid throughthe sterile loop 50. The pump includes pump components in the housing 15and an external rotary input or rotary driving element 101 (FIG. 7)which is part of the calibration apparatus 21. The pump components inthe housing 15 include a curved wall surface 103 (FIG. 4), thecompressible tube 71 and a tube compressor 105. The opposite ends of thetube 71 form an inlet and an outlet, respectively, for the pump.

More particularly, the wall surface 103 in this embodiment iscylindrical and constitutes the inner surface of a cylindrical boss 107,portions of which are formed integrally with the cover 65 and the topsection 67. The tube compressor 105 is surrounded by the wall surface103, and the tube 71 is wrapped in a circumferential direction about onetime around the tube compressor and lies between the tube compressor andthe wall surface 103.

The cover 65 and the top section 67 have flanges 109 and 111,respectively, which provide retaining surfaces for restraining the tubecompressor 105 against axial movement relative to the wall surface 103.Because there is a radial clearance between the tube compressor 105 andthe wall surface 103 and because the flanges 109 and 111 do not restrainthe tube compressor against radial movement, the tube compressor ismounted on the housing for free radial movement relative to the wallsurface 103 and the boss 107. In other words, the tube compressor 105can be moved radially in any direction from the centered or neutralposition shown in FIG. 4, with the only consequence being the squeezingof the compressible tube 71. With this construction, the tube compressor105 can be caused to roll along the tube 71 to squeeze the tube in azone which moves along the tube to thereby pump fluid in the tube. Inthe neutral position, the tube 71 is not squeezed.

The tube compressor 105 is generally cylindrical and tubular and has anoutwardly opening cavity 113 having a mouth 115 which is flared radiallyoutwardly to receive the rotary input 101 as described hereinbelow.Thus, the cavity 113 provides means on the tube compressor 105 for usein releasably drivingly coupling the tube compressor to the externalrotary element 101 whereby the tube compressor can be rolled along thetube 71 to pump fluid in the tube. The tube compressor 105 isconstructed of a suitable rigid material, such as a rigid plastic, andthe cavity 113 is defined by a smooth, hard, low-friction surface whichsurface is smoother, harder and of substantially lower friction than thetube 71. This facilitates reception of the rotary driving element 101,which is also smooth and hard and provides a low-friction surface.

The tube compressor 105 also has an annular flange 116 at the opening ofthe mouth 115. The flange 116 cooperates with the flange 109 to closethe upper end of a compartment 118 between the tube compressor 105 andthe wall surface 103 so that the tube 71 cannot escape out the upper endof the compartment regardless of the radial position of the tubecompressor 105.

The tube 71 has opposite end portions 120 having regions 122 whichextend generally tangentially of the tube compressor 105 and regions 124which extend axially of the tube compressor 105 to their respectiveends. Each set of the regions 122 and 124 is integrally joined by a90-degree bend portion. The tangential regions 122 have annular flanges126 which are captured as shown in FIG. 4 by the boss 107 and adjacentregions of the top section 67 to thereby hold the tube 1 in position.

To prevent leakage of the sterile calibration fluid, it is important toseal the opposite ends of the tube 71 to the confronting portions of thecover 65. This can advantageously be accomplished with the sealconstruction shown in FIG. 4A. As shown in FIG. 4A, the tube 71 has anannular flange 117 at each end and a tube passage 119, which forms aportion of the liquid passage 41, extending longitudinally through thetube and opening at its opposite ends. The tube 71 and its flanges 117are constructed of a resilient elastomeric material, such as siliconerubber, and as such are deformable. By forming the tube 71 of suchresilient elastomeric material, the tube is capable of being compressedby tube compressor 105 of the pump so as to move fluid through thecompressible tube 71, and hence, through the rest of the fluid pathwayformed within apparatus 11. Each of the flanges 117 has an outer face121 and an inner face 123.

The cover 65 has flange-supporting faces 125 surrounding the apertures73 and 77, respectively. The outer face 121 of each of the flanges 117engages the associated flange-supporting face 125 with the apertures 73and 77 being in registry with the passage 119.

The tube 71 is received by a rigid clamp ring 127 of metal or rigidplastic and by a portion of the top section 67, and these memberscooperate to form a tube-receiving structure which is coupled to thecover 65. The clamp ring 127 has an annular projection 129 which engagesthe inner face 123. The annular projection 129 is radially narrower thanthe inner face 123 of the flange 117 and provides high-unit loading ofthe flange to deform the flange. The annular projection 129 urges theflange 117 tightly against the supporting face 125 to provide afluid-tight seal along the juncture of the tube passage 119 and theaperture 73. The top section 67, when coupled to the cover 65, urges theclamp ring 127 toward the flanges 117. As shown in FIG. 4A, the annularprojection 129 deforms the flange 117 with some of the material of theflange flowing upwardly around the annular projection. In its undeformedconfiguration, the inner face 123, as well as the outer face 121, areplanar, although a planar configuration is not required.

The cover 65 has wells 131 for receiving the flanges 117, with theflange-supporting faces 125 being at the end or bottom of the associatedwells. The wells 131 open at circumscribing surfaces 133, and the clamprings 127 are spaced from the surfaces 133, respectively. With thisconstruction, all of the force applied to the clamp rings 127 by the topsection 67 is used to deform the associated flange 117 to effect a tightseal, and none of this force is taken up by the underlying surfaces 133.

More specifically, the top section 67 has a shoulder 134 which contactsthe clamp ring 127 to force it downwardly (as viewed in FIG. 4a) againstthe flange 117. The shoulder 134 contacts the clamp ring 127 around lessthan 360 degrees, and in the embodiment illustrated, this contact regionis a little over 180 degrees. However, because the clamp ring 127 isrigid, it operates to apply a squeezing force to the flange 117 around afull 360 degrees of the flange. As evidenced previously, in theirundeformed configuration, each of flanges 117 preferably has arelatively flat, planar configuration. It is only upon deforming flange117 by annular projection 129 to form the fluid-tight seal that aportion of the flange 117 flows upwardly around the annular projection129 and into well 131 as shown in FIG. 4a. This may be furtherunderstood by reference to FIG. 4a where it is seen that the lowestsurface of annular projection 129 is an annular contacting face 128horizontal to the page, and that the annular projection 129 has a sideface 130 directly adjacent and perpendicular thereto. Prior to thecondition illustrated in FIG. 4a (not shown), i.e., prior to loading theflange 117 and deforming the flange 117 to create the fluid-tight sealdisclosed herein, the periphery of flange 117, defined where inner face123 and outer face 121 meet, extends beyond the annular contacting face128 of annular projection 119 such that the inner face 123 of the flange117 is in contact with the annular contacting face 128 of the annularprojection 119, but not with the side face 130 thereof. As seen in FIG.4a, which illustrates the seal construction after deformation of theflange 117, after flange 117 has been deformed, the inner face 123 ofthe flange 117 also contacts the side face 130 of the annular projection119 since the flange 117 has been deformed upwardly into well 131.

As shown in FIGS. 2-4, the gas-injection port 52, the temperature well97 and the tube compressor 105 all open at the exterior of the housingon the same side of the housing. In addition, the housing 15 has a well135 defined by an upstanding annular boss 137, and the well also openson the same side of the housing. The well 135 surrounds thegas-injection port 52.

The calibration apparatus 21 includes a supporting structure 141 and adoor 143 pivotally mounted on the supporting structure for movementbetween an open position shown in FIG. 7 and a closed position shown inFIG. 8. The rotary driving element 101 is rotatably mounted on thesupporting structure 141 and projects outwardly from a front surface 145thereof. The rotary driving element 101 is an eccentrically mounted camwhich is rotatable about an axis 146 (FIG. 9). In this embodiment, therotary driving element 101 is driven by a suitable motor 147, which isalso carried by the supporting structure 141. The rotary driving member101 serves as a cam to move the tube compressor 105 to bring about apumping action in the tube 71.

A tube 149 carrying an annular seal 151 and defining a gas exit port 153is mounted on the supporting structure 141 and projects outwardly fromthe front surface 145 in the same direction as the rotary drivingelement 101. A temperature sensor in the form of a temperature probe 155is also mounted on the supporting structure 141 and projects outwardlyfrom the front surface 145 in the same direction as the rotary drivingelement 101. The tube 149 is coupled to a source 156 of calibration gas,which also may be carried by the supporting structure 141. Thetemperature probe 155 may be coupled to an appropriate temperature readout (not shown) and/or to a circuit for controlling a heat lamp 157which is carried by the supporting structure 141 and faces outwardlyfrom the front surface 145 in the same direction as the rotary drivingelement 101. The heat lamp 157 is provided for the purpose ofmaintaining the calibration liquid 16 at the desired temperature, suchas 37 degrees C.

A spring-biased ejector 159 is mounted on the supporting structure 141and projects outwardly from the front surface 145. When the housing 15is positioned on the supporting structure 141 as described below and thedoor is in the closed position of FIG. 8, the ejector 159 applies aresilient force to the housing to urge the door toward the open positionof FIG. 7.

The entire disposable component of the system 11 as shown in FIG. 1 iscarried in an openable package 161 (FIGS. 7 and 9). The package 161includes a cover 163 which can be peeled back as shown in FIG. 7 toexpose the portions of the system 11 carried by the package. The door143 has a recess 165 for receiving the package 161. The package 161 andthe recess 165 have sufficiently complementary configurations so thatthe recess can at least assist in releasably retaining the package in apredetermined orientation. The housing 15 is retained within the package161 in a predetermined orientation by a projection 167 in a bottom wall169 of the package 161 and a mating recess 171 (FIG. 9) in the housing.

In use, the cover 163 is peeled back from the remainder of the package161, and the package is placed in the recess 171 of the door 143 asshown in FIG. 7. An optical head 172 is coupled to the sensor cassette13 in a known manner to optically couple the sensors 29, 31 and 33 to aninstrument or monitor 175. The closure caps 53 and 57 are removed toexpose the gas injection port 52 and the gas vent 55, respectively. Thedoor 143 is then pivoted from the open position of FIG. 7 to the closedposition of FIG. 8, and the door is retained in the closed position by asuitable lock 173.

Placing the door 143 in the closed position positions the housing on thesupporting structure 141. When so positioned, the rotary driving element101, the tube 149 and the temperature probe 155 are received in thecavity 113, the well 135 and the temperature well 97, respectively, andthis results automatically from simply closing the door, i.e., movingthe door to the closed position. In addition, the ejector 159 isresiliently compressed against a region of the housing 15 so that theejector resiliently loads the door 143 toward the open position of FIG.7.

The flared mouth 115 serves as a cam follower or lead in as the rotarydriving element 101 is inserted into the cavity 113. Specifically, therotary driving element 101 cooperates with the flared mouth 115 to camthe tube compressor 105 radially to the position shown, by way ofexample, in FIG. 9 in which one side of the tube 71 is tightly squeezedbetween the tube compressor and the curved wall surface 103, and theother side of the tube 71 is uncompressed.

The rotary driving element 101 has a nose 177 (FIG. 9) which is receivedin a bearing 179 when the door is in the closed position.

It will be appreciated that the tube compressor 105 is in the neutralposition during storage of the housing 15 and at all times when therotary driving element 101 is not received within the tube compressor105 as shown in FIG. 9. Consequently, the tube 71 is normally notcompressed, or significantly compressed. Consequently, there is nodanger of the tube 71 taking a "set" or becoming occluded as a result ofcompression of the tube during storage. Because the tube compressor 105is free to move radially inside the curved wall surface 103, eccentricrotation of the rotary driving element 101 about the axis 146 (FIG. 9)causes the tube compressor 105 to roll along the tube to create aperistaltic pumping action to pump the calibration liquid 16 through thesterile loop 50 including the flow-through passage 23 of the housing 15.Because the surfaces defining the cavity 113 and the exterior of therotary driving element 101 are relatively hard, smooth and of lowfriction, the insertion of the rotary driving element 101 into thecavity 113 is easily accomplished by simply closing the door 143 eventhough a camming action and consequent radial movement of the tubecompressor 105 must occur.

It should be noted that no angular indexing of the rotary drivingelement 101 is necessary in order to insert the rotary driving elementinto the cavity 113 of the tube compressor 105. Thus, driving engagementcan be established between the rotary driving element 101 and the tubecompressor 105 automatically as a result of moving the door 143 to theclosed position and regardless of the angular orientation of the rotarydriving element 101.

The closing of the door 143 also inserts the tube 149 into the well 135to place the gas exit port 153 in communication with the gas injectionport 52 as shown in FIG. 10. The seal 151 cooperates with the well 135to maintain a gas-tight seal between the tube 149 and the boss 137 overa range of insertion depths. Consequently, gas can be supplied from thegas source 156 through the gas exit port 153, the gas injection port 52,the passage section 85 (FIG. 2) to the chamber inlet section 75 at the"T" 84. The gas is supplied at some positive pressure, and consequently,the pressure in the liquid passage 41 is greater than ambient. For thisreason, gas vents from the gas vent 55, and the positive pressureexisting in the liquid passage 41 and the flow of gas outwardly inhibitsinward flow of gas or liquid through the gas vent 55 into the liquidpassage 41. At the "T" 84, the gas is introduced into the stream ofcalibration liquid 16 being circulated by the pump and is premixed withthe liquid for introduction into the sparging chamber 47. The gas issterilized by the filter 81 so that sterile gas is introduced into thesterile calibration liquid 16. Gas which vents from the vent 55 canescape from within the calibration apparatus 21.

In the closed position of the door 143, the temperature probe 155 isreceived within the well 97 so that temperature readings can be taken ofthe liquid in the outlet passage section 95. In addition, the heat lamp157 is placed in close proximity with the housing 15 so that thecalibration liquid 16 can be heated to the desired temperature.

When the partial pressures of the gases of interest reach the desiredlevel in the calibration liquid 16, the monitor 175, is calibrated tothe particular sensor cassette 13 and, particularly, the sensors 29, 31and 33 thereof using conventional techniques. Thereafter, lock 173 isunlocked, and the door 143 is pivoted to the open position by theejector 159 to remove the housing 15 from the calibration apparatus 21.The sensor cassette 13 can be employed with the monitor 175 for themeasurement of the relevant blood parameters of interest of a patient asdisclosed, for example, in U.S. Pat. application Ser. No. 229,617referred to above.

Although an exemplary embodiment of the invention has been shown anddescribed, many changes, modifications and substitutions may be made byone having ordinary skill in the art without necessarily departing fromthe spirit and scope of this invention.

We claim:
 1. An apparatus comprising:a pump having a fluid pathwaytherein; a compressible tube made of resilient elastomeric material,said tube having an annular flange at one end thereof and a passageextending longitudinally in the tube and opening at said one end of thetube, said passage forming at least a portion of the fluid pathway andsaid tube being capable of being compressed by said pump to move fluidthrough the passage and fluid pathway, said flange being made ofresilient elastomeric material and being deformable and integral withthe tube, said flange having outer and inner faces; a first memberhaving an opening and a flange supporting face surrounding said opening,said outer face engaging said flange supporting face with said openingbeing in registry with said passage to form a juncture of the passageand the opening; and a tube receiving structure receiving said tube andcoupled to the first member and including means defining an annularprojection engaging said inner face of said flange; said annularprojection being radially narrower than the inner face of the flange andproviding high-unit loading of the flange to deform the flange, saidannular projection urging the flange tightly against the supporting faceto provide a fluid-tight seal around the juncture of the passage and theopening.
 2. An apparatus as defined in claim 1 wherein the meansdefining an annular projection includes a clamp ring receiving said tubeand the tube receiving structure includes a second member coupled to thefirst member and urging the clamp ring toward the flange.
 3. Anapparatus as defined in claim 2 wherein the first member has a well forreceiving the flange with the flange supporting face being at an end ofthe well.
 4. An apparatus as defined in claim 3 wherein the first memberhas a first surface and the well opens into the first surface, saidclamp ring being spaced from the first surface.
 5. An apparatus asdefined in claim 1 wherein, prior to deformation, said flange has arelatively flat, planar configuration.
 6. An apparatus as defined inclaim 5 wherein the annular projection has an annular contacting faceand a side face, wherein the inner and outer faces of the flange meet ata periphery, and wherein, prior to deformation of the flange, theperiphery of the flange extends beyond the annular contacting face ofthe annular projection such that the inner face of the flange is incontact with the annular contacting face of the annular projection butnot with the side face thereof.
 7. An apparatus as defined in claim 6wherein, after deformation of the flange, the inner face of the flangealso contacts the side face of the annular projection.
 8. An apparatusas defined in claim 7 wherein said tube and said flange are made ofsilicone rubber.
 9. An apparatus as defined in claim 1 wherein theannular projection has an annular contacting face and a side face,wherein the inner and outer faces of the flange meet at a periphery, andwherein, prior to deformation of the flange, the periphery of the flangeextends beyond the annular contacting face of the annular projectionsuch that the inner face of the flange is in contact with the annularcontacting face of the annular projection but not with the side facethereof.
 10. An apparatus as defined in claim 9 wherein, afterdeformation of the flange, the inner face of the flange also contactsthe side face of the annular projection.
 11. An apparatus as defined inclaim 10 wherein said tube and said flange are made of silicone rubber.12. An apparatus as defined in claim 1 wherein said tube and said flangeare made of silicone rubber.
 13. An apparatus as defined in claim 12wherein prior to deformation, said flange has a relatively flat, planarconfiguration.